Wrong type definition

[cawa-93]

TypeScript Version:
1.9.0
Atom-TypeScript plugin Version:
8.11.0
Atom Version:
1.7.4
Code method of Class

setProfiles(newProfiles: IProfiles[]) {
    let needSearch = true;
        // By default, the variable is of type
        // this.stg.profiles: IProfiles[] | undefined
    if (!this.stg.profiles) {
        this.stg.profiles = [];
        needSearch = false;
    }
    // On the line below the variable type is defined as
    // this.stg.profiles: IProfiles[]
    if (!angular.isArray(newProfiles)) return this.stg.profiles;

    newProfiles.map((profile) => {
        if (!profile || !profile.id) return;
        const index = needSearch ? this.getProfileIndex(profile.id) : -1;

        if (index >= 0) {
            // However, on the line below the variable type is defined as
            // this.stg.profiles: IProfiles[] | undefined
            this.stg.profiles[index] = profile;
        } else {
            // And in the line below too
            // this.stg.profiles: IProfiles[] | undefined
            this.stg.profiles.unshift(profile);
        }
    });

    // Agin, On the line below the variable type is defined as
    // this.stg.profiles: IProfiles[]
    return this.stg.profiles;
}

As you can see from the comments, the type of a variable is not defined clearly in the callback function.
Why is this happening? How can I fix it?

[kitsonk]

Dupe of #7662 as narrowing is reset across function boundaries as explained in #7718 (comment).

[cawa-93]

@kitsonk, thanks for the answer